[helly25]

Prepare the repository for development after the 0.16.0 release.

AG;DR

• Bump the module version from 0.16.0 to 0.16.1.
• Add the empty 0.16.1 changelog section for subsequent changes.
• Created automatically by tools/trigger_release.sh; this PR still requires normal review.
• The signed commit is verified by GitHub and is based on the exact main commit tagged for 0.16.0.
• Validation on the unchanged, current pushed head: the full 25-job Test workflow passed, including the explicit aggregate done gate, compiler/sanitizer matrix, independent release-archive consumers, pre-commit, Trunk and release-site tests. Separate coverage integrity also passed.
• No release artifacts, public APIs, compiler requirements or portability behavior change here.